They didn't just go out and build some. The KGB was stealing NASA's plans. NASA caught on (with help from CIA) and implanted falsified heat tile formulas, which the Soviets copied. Their first Buran only flew once and mostly burned up on reentry due to the bad heat tiles. The Soviets copied most of the design but used their own engine.[1] Then the USSR collapsed. Currently they are sitting in decaying hangars in Baikonur, just rotting away. There's video on youtube of people sneaking in (it's a guarded base), flying drones around them and climbing around in and out of them. It's pretty cool. [2]
[1] https://www.discovermagazine.com/the-sciences/real-life-rogu...
[2] https://www.youtube.com/watch?v=-q7ZVXOU3kM